Intra-aortic balloon pumping is a recognized method of cardiac assistance for a failing heart. The original indications for intra-aortic balloon pumping in cardiogenic shock due to acute infarction, post-operative severe low cardiac output state, or inability to wean from cardiopulmonary bypass have been extended to include treatment for refractory unstable angina in the period before and after infarction, recurrent life-threatening tachyarrhythmias, preoperative support in the presence of severe left ventricular dysfunction and reduction of infarct size.
During the first few years following the introduction of the intra-aortic balloon pump for clinical use in 1968, balloon catheters were the subject of considerable development and design efforts. In the 1970's, most of the efforts in the field of intra-aortic balloon pumping were directed mainly toward clarifying the indications for and to reporting large clinical experiences with this therapeutic modality. During this period, no major advances in balloon catheter technology were made.
Catheter for intra-aortic balloon pumping typically have utilized a nonstressed or nondistendable balloon, i.e., the balloon is not stretched during inflation and deflation and doesn't substantially change its surface area, inflating and deflating with a predetermined volume of appropriate fluid to achieve phasic operation; the balloon surface area is always substantially equal to that of a fully inflated balloon.
It has been recognized in the prior art that insertion and guiding of catheters in patients is difficult and that trauma and damage to the incision and blood vessel may occur during said insertion and guiding. In some prior art catheters, in order to permit insertion and guiding of the catheter in a blood vessel, the balloon is rolled or spirally wrapped around its underlying central lumen. See for example, FIGS. 3 and 4 of Goetz et al., U.S. Pat. No. 3,692,018. This makes the catheter more compact. In Grayzel, U.S. Pat. No. 3,939,820, the size of the catheter can be reduced by replacing the catheter tube within the balloon by a wire. However, the balloon is nonetheless spirally wrapped around the wire. Additionally, the wire in Grayzel is relatively inflexible to support the balloon.
Insertion of the balloon catheter is conventionally performed in accord with the standard Seldinger technique which is a non-surgical insertion through the skin (percutaneously) developed in the late 1950's. One type of known percutaneous intra-aortic balloon catheter comprises a single chamber balloon sealably disposed at the end of a catheter. The extreme end of the balloon is internally bonded to a stiff wire disposed within the balloon and which terminates at a swivel located at the junction of the catheter and the balloon. The balloon is wrapped around the wire by grasping the catheter and twisting the remote end of the balloon until the desired degree of wrapping is obtained. After the balloon is wrapped the application of a vacuum to the interior of the balloon is relied on to maintain the balloon in its wrapped condition. Neither during nor after insertion is access to the interior of the aorta available. Application of pressure to the interior of the balloon, together with manual rotation of the catheter, is relied on to effect unwrapping of the balloon and permit pumping to begin.
Other balloon catheters having additional mechanical features such as flexible tips, elongating tips, rotating members, etc. have been described in, for instance, U.S. Pat. Nos. 4,261,339; 4,276,874; 4,327,709; 4,346,698; 4,362,150 and 4,402,307.
However these prior art balloon catheters are typically made with stiff surgical steel tubes, with or without flexible tips to lessen or prevent trauma to the blood vessel during insertion, or from flexible polymeric tubing which has no positive torque transmission capability. The first type balloon catheters are uncomfortable in the patient and care must be taken by the patient to avoid trauma. A guide wire is required for insertion. The second type is relatively comfortable after insertion but lacks positive control of the unwrapping of the balloon due to the resilient nature of the polymeric tubing under rotational force and to the inability of such tubing to transmit positive torque. Thus, these type balloon catherers require a stylet to assure unwrapping. However, certain situations require a guide wire for insertion into the patient. The use of a guide wire and a stylet are mutually exclusive. Thus, a majority of the balloons having a soft central lumen do not unwrap properly when the wrapping stylet is removed. Incomplete unwrapping can cause clotting.
Thus, it can be seen that it would be highly desirable to have a balloon catheter with the flexible properties of the polymeric tubing central lumen to increase comfort while providing positive rotational torque transmission to insure complete unwrapping of the balloon after insertion.